1. Field of the Invention
This invention relates to a portable grinder such as an electric portable disk grinder.
2. Description Of the Prior Art
Electric portable disk grinders have a grinding wheel detachably mounted on a rotatable spindle or shaft. Specifically, a threaded flange in mesh with a threaded portion of the spindle is used to fix the grinding wheel to the spindle. When the threaded flange is rotated by a wrench or spanner in a forward direction, the grinding wheel is fastened to the spindle. As the threaded flange is reversed by the wrench, the grinding wheel is released.
During a grinding process, when the grinding wheel is subjected to an excessively great load, the threaded flange fastens the grinding wheel to the spindle by a greater torque. In such a case, to detach the grinding wheel from the spindle after the grinding process has been completed, a greater return torque needs to be applied to the wrench.
Japanese published unexamined patent application 4-343662 discloses an electrically-powered tool in which a rotatable blade is detachably mounted on a spindle by a fastening device. The fastening device is designed to provide secure attachment of the blade to the spindle but enable easy detachment of the blade therefrom.